The present invention relates to receiver down converters and more particularly to receiver down converters for use in radiotelephones and radiotelephone equipment.
With ever increasing demands for increased talk time and standby time in wireless telephones, the power consumption of each circuit in the telephone can be critical to the overall performance of the telephone. Thus, it has become more important to assure that each circuit uses as little current as possible to thereby extend battery life of the telephone.
While reducing power usage in the telephone is important, this goal is generally at odds with other performance goals for the telephone. For example, as the number of wireless telephone users utilizing fixed amount of radio spectrum increase, the need to reject undesired interference can become very important. However, when operating in strong signal environments higher current is generally required by the down converter of the telephone receiver to compensate for the strong signal environment.
In particular in wireless telephone modes such as Code Division Multiple Access (CDMA) mode the linearity of the low noise amplifier, as reflected by the third order intercept point of the amplifier, may be critical to meeting the requirements of CDMA. However, increasing the third order intercept point to increase the linearity of the amplifier generally requires an increase in the current drawn by the amplifier. Thus, the requirements of CDMA may directly conflict with the goal of low power consumption.
Previous attempts to address the strong signal condition have included switching off the low noise amplifier of the receiver down converter. When the low noise amplifier is switched off it acts like an attenuator which would increase the signal handling ability of the telephone. Furthermore, since the low noise amplifier is off the power consumed may be reduced. However, such an approach not meet the performance requirements of CDMA.
Other possible solutions to the strong signal problem may include switching an attenuator in the signal path in the down converter. While this solution may provide a solution to the strong signal problem it would not reduce the power consumption of the down converter.
Similarly, down converter integrated circuits have been developed to accommodate multi-mode wireless telephones. Thus, for example, the RF Micro Devices RF9906 down converter includes adjustable mixer gain which allows for high gain to overcome the higher filter loss of CDMA mode and a low gain for use in AMPS/DAMPS mode. Similarly, the RF9986 device of RF Micro Devices allows for strong signal conditions in CDMA mode by having a switchable third order intercept point which may be increased by 10 db by connecting Vcc to the IP3 pin of the device which causes the LNA current consumption to increase by 10 mA. While these devices allow the wireless telephone to meet the various requirements of the modes of operation of the wireless telephone, there continues to be a need to reduce the down converter""s power requirements while still meeting the operational requirements of the wireless telephone.
In view of the above discussion, there exists a need for improvement in power management in wireless telephones while still meeting the signal handling requirements of the modes of operation of the wireless telephone.
In view of the above discussion, it is an object of the present invention to allow reduced power consumption of a down converter.
A further object of the present invention is to provide a down converter capable of handling strong signal conditions.
Still another object of the present invention is to allow an increase in the battery life of radiotelephones.
Another object of the present invention is to provide a down converter with reduced power consumption in multiple modes of operation of a radiotelephone.
These and other objects of the present invention are provided by methods and systems which control the operation of a receiver of a radiotelephone so as to reduce the power consumption of the receiver by setting the third order intercept point of a low noise amplifier based upon at least one of a strength of a signal received by the radiotelephone or a transmission power of a transmitter of the radiotelephone. Furthermore, the gain of the low noise amplifier may also be set based upon the received signal strength or the transmission power of the transmitter of the radiotelephone. Also, the gain of an amplifier associated with a mixer of the receiver of the radiotelephone may be set based upon the strength of the signal received by the radiotelephone or the transmission power of a transmitter of the radiotelephone.
By adjusting the third order intercept and/or gain of the low noise amplifier and the gain of the mixer amplifier based on the transmitter power or the received signal strength, the performance of the down converter may be adjusted to the operating conditions of the telephone. Furthermore, the gains and third order intercept point may be adjusted to reduce the power consumption of the down converter. Thus, as the signal strength increases the performance of the down converter may be maintained while reducing the power required by the down converter. The total power required to operate the radiotelephone may be decreased and battery life correspondingly increased.
In certain embodiments of the present invention the gains of the low noise amplifier and mixer amplifier of the down converter may be set by bypassing the amplifiers. Thus, the gains are selected between two gain levels for the amplifiers.
In particular embodiments of the present invention, the third order intercept point of the low noise amplifier is set to a low third order intercept point, the gain of the low noise amplifier to a high gain and the gain of the mixer amplifier to a high gain if the transmitter is off.
In alternative embodiments of the present invention in which the radiotelephone is operating in CDMA mode, if the transmitter is operating at an output power above a predefined threshold or the received signal strength is below a predefined threshold, the third order intercept point of the low noise amplifier may be set to a high third order intercept point, the gain of the low noise amplifier set to a high gain and the gain of the mixer amplifier set to a high gain. If the transmitter is operating at an output power below the predefined threshold or the received signal strength is above a predefined threshold, the third order intercept point of the low noise amplifier may also be set to a high third order intercept point, the gain of the low noise amplifier set to a high gain and the gain of the mixer amplifier set to a low gain. The third order intercept point of the low noise amplifier may also be set to a high third order intercept point, the gain of the low noise amplifier set to a high gain and the gain of the mixer amplifier set to a low gain if the transmitter is operating at an output power below the predefined threshold output power and the received signal strength is greater than a first predefined signal strength threshold and less than a second predefined signal strength threshold. The gain of the low noise amplifier may be set to a low gain and the gain of the mixer amplifier set to a high gain if the transmitter is operating at an output power below the predefined threshold output power and the received signal strength is greater than the second predefined signal strength threshold and less than a third predefined signal strength threshold. Finally, the gain of the low noise amplifier may be set to a low gain and the gain of the mixer amplifier to a low gain if the transmitter is operating at an output power below the predefined threshold output power and the received signal strength is greater than the third predefined signal strength threshold.
By providing several thresholds of power conservation, the present invention may provide the high linearity required by the CDMA mode of operation while still reducing the total power consumed by the down converter. Thus, the present invention can allow the down converter to meet the performance criteria of CDMA while still conserving power.
In another embodiment of the present invention, the receiver of the radiotelephone is disabled if the radiotelephone is in sleep mode.
In an embodiment of the present invention where the radiotelephone is operating in Advanced Mobile Phone Service/Digital Advanced Mobile Phone Service(AMPS/DAMPS) mode, the third order intercept point of the low noise amplifier may be set to a low third order intercept point, the gain of the low noise amplifier set to a high gain and the gain of the mixer amplifier set to a low gain if the received signal strength is less than a first predefined signal strength threshold. The third order intercept of the low noise amplifier may be set to a low third order intercept point, the gain of the low noise amplifier set to a high gain and the gain of the mixer amplifier set to a low gain if the received signal strength is greater than the first predefined signal strength threshold an less than a second predefined signal strength threshold. The gain of the low noise amplifier may also be set to a low gain and the gain of the mixer amplifier set to a low gain if the received signal strength is greater than the second predefined signal strength threshold.
In still another embodiment of the present invention, the operation of a receiver of a radiotelephone so as to reduce the power consumption of the receiver by determining the received signal strength of a signal received by the radiotelephone and controlling the power consumption of a down converter of the receiver of the radiotelephone based upon the determined received signal strength. This determination may include determining if the received signal strength is above a first threshold value, if the received signal strength is between the first threshold value and a second threshold value and if the received signal strength is above the second threshold value. The gain of the low noise amplifier may then be set to a low gain and the gain of the mixer amplifier to a low gain if the signal strength is above the second threshold value, the gain of a low noise amplifier of the down converter set to a high gain and the gain of a mixer amplifier of the down converter set to a low gain if the received signal strength is between the first threshold value and the second threshold value and the gain of a low noise amplifier of the down converter set to a high gain and the gain of a mixer amplifier of the down converter set to a high gain if the received signal strength is below the first threshold value. In a particular embodiment, the first threshold value is about xe2x88x9294 dBm, and the second threshold value is about xe2x88x9260 dBm.
By controlling the gains of amplifiers in AMPS/DAMPS mode based upon several threshold values the power consumption of the down converter may be reduced without sacrificing performance.